How to build a wicking bed

 

I receive a great number of enquiries for practical information on how to build a wicking bed.

 First step is to study the files on my web site.  If you go to INDEX you will see files listed in time order and subject.  It is a good idea to look at the time order as this shows the new files at the top so you will see the latest information.

 You should particularly look at wicking_bed_technology.pdf as this explains the theory of wicking beds.

 Next step is to decide whether you want an open or closed wicking bed.  Open wicking beds are built on or in the ground, while the closed wicking beds are usually in some from of box and are isolated from the ground.

 Open wicking beds, are suited to larger beds and are typically around 20 meters long.  They are much cheaper to build; the soil is in contact with the natural soil which helps develop micro biological activity. Water can wick out into the surrounding soil so more care is needed in scheduling to avoid waste of water; this can be turned to advantage by growing trees, close to the bed to mop up any water.  You do need to check that you are not watering too often, if the soil surrounding the beds is wet deep into the ground then you are watering too often.

Closed wicking beds are usually built in a box or container of some sort and are therefore more expensive usually smaller, up to say 3 meters.  There is no contact with the surrounding soil so you have to add the micro biology yourself.

There is no loss of water to the surrounding soil so all you have to do is to fill up the water reservoir when it is empty.

The best way of making one type of open wicking bed is shown in bed under construction.  Simply remove about 300 mm of the top soil.  Check the bed is level, lay in the plastics liner and pipes and fill to the surface level with organic waste.  Wood chips, sugar cane mulch etc are fine.  Now replace the top soil so the top of the bed is some 300mm above ground level.

Here you have an option. You can simply lay the soil so it forms a bank which connects the wicking bed soil to the natural soil allowing the micro organisms to migrate into the bed. Alternatively you can build some sort of fence form wooden logs or shade cloth to hold the soil in place with no contact with the natural soil so it becomes in effect a closed bed.

As the beds are best built on the contour line it is a good idea to make sure there is drainage around the ends of the bed so the whole area does not flood.

Closed wicking beds are built in a water proof container in the same way as the open bed.  But it is essential to provide drainage for the soil layer.  Drilling a hole in the side of the box is one way but small holes get blocked up.  Make several big holes (10+mm) around the bed and line with shade cloth or similar to stop the soil leaking out.

Alternatively you can line the box with shade cloth and use a stick or pipe outside the shade cloth for excess water to drain away

 If the soil looks water logged then you do not have enough drainage and your plants will not grow.  The beds made from shade cloth are probably the best.

Some people want to use sand for the lower layer thinking that it will last longer than organic material.  Sand certainly works but will eventually silt up.  Organic material is preferred, it is mostly immersed in water so does not decompose like a compost heap.  Rather it forms a compost tea which is highly nutritious.  However wood chips will reduce the available nitrogen levels so it is best to add extra nitrogen, such as blood and bone.

The surface of the bed should be dry.  When you plant seeds you can wet the surface, after they have germinated and developed a root system you only water from the pipes.

 When you harvest your crop you can dig a hole in the bed down to near the plastics and spread this decomposed material on the surface of the bed.  Then refill the hole with fresh organic material.  Next time dig your hole in a different spot so you are continuously replacing the organic material.

You can also view wicking bed.ppt which is the power point presentation I will be giving in China.  This is a big file which may take time to load, best to save rather than open.

 

 

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